Lithium niobate nanophotonic structures have recently become a promising candidate for efficient nonlinear frequency-conversion processes. Here, the second harmonic generation in a graphene-based LN waveguide is theoretically proposed at the telecommunication band. The structure is able to gain high conversion efficiency due to the large nonlinear coefficient of LN and tight field confinement. The subwavelength mode confinement inside the LN layer is strongly influenced by the graphene conductivity. In the presented structure, the nonlinear interaction of propagating plasmons can be widely tuned by slightly change in the surface conductivity of graphene monolayer which is a promising feature for SHG applications in comparison to the conventional structures which rely on geometry variation. According to the results, SH intensity of \(I_{{{\text{SH}}}} = 0.09\,{\text{kW}}/{\text{cm}}^{2}\) is observed at the fundamental wavelength of \(1550\,{\text{nm}}\) with a 7% of nonlinear conversion efficiency. To analyze the geometrical parameters and show the tunability of the configuration, the effect of input frequency and waveguide length on SH output power are demonstrated at \(P_{{{\text{FF}}}} = 1W\) and μ_c = 0.6 eV. The calculations reveal that the \(P_{{{\text{SH}}}}\) becomes lower by lengthening the waveguide where the maximum output of \(P_{{{\text{SH}}}} = 72.5\,{\text{mW}}\) is obtained at 1 μm-long waveguide.

铌酸锂纳米光子结构最近已成为高效非线性频率转换过程的有希望的候选者。在这里，理论上在电信频段提出了基于石墨烯的 LN 波导中的二次谐波生成。由于LN的大非线性系数和紧密的场限制，该结构能够获得高转换效率。LN 层内的亚波长模式限制受石墨烯电导率的强烈影响。在所提出的结构中，传播等离子体激元的非线性相互作用可以通过石墨烯单层表面电导率的轻微变化来广泛调整，与依赖几何变化的传统结构相比，这是 SHG 应用的一个有前途的特征。根据结果​​，SH强度为\(I_{{{\text{SH}}}} = 0.09\,{\text{kW}}/{\text{cm}}^{2}\)在\(1550\ ,{\text{nm}}\)具有 7% 的非线性转换效率。为了分析几何参数并显示配置的可调谐性，输入频率和波导长度对 SH 输出功率的影响在\(P_{{{\text{FF}}}} = 1W\)和μ _c  = 0.6 电子伏特。计算表明\(P_{{{\text{SH}}}}\)通过延长波导而变得更低，其中\(P_{{{\text{SH}}}}}的最大输出为72.5\， {\text{mW}}\)在 1 μm 长的波导处获得。